package com.ndp.fb.util;

/**
 * Created by jacky.cheng on 2016/2/25.
 */
public class CamelCaseUtils {

    private static final char SEPARATOR = '_';

    /**
     * snake_case
     * @param s
     * @return
     */
    public static String toSnakeCase(String s) {
        if (s == null) {
            return null;
        }
        StringBuilder sb = new StringBuilder();
        boolean upperCase = false;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            boolean nextUpperCase = true;
            if (i < (s.length() - 1)) {
                nextUpperCase = Character.isUpperCase(s.charAt(i + 1));
            }
            if ((i >= 0) && Character.isUpperCase(c)&&!nextUpperCase) {
                if (!upperCase) {
                    if (i > 0) sb.append(SEPARATOR);
                }
                upperCase = true;
            } else {
                upperCase = false;
            }
            sb.append(Character.toLowerCase(c));
        }
        return sb.toString();
    }

    /**
     * camelCase
     * @param s
     * @return
     */
    public static String toCamelCase(String s) {
        if (s == null) {
            return null;
        }
        s = s.toLowerCase();
        StringBuilder sb = new StringBuilder(s.length());
        boolean upperCase = false;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (c == SEPARATOR) {
                upperCase = true;
            } else if (upperCase) {
                sb.append(Character.toUpperCase(c));
                upperCase = false;
            } else {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    /**
     * UpperCamelCase/PascalCase
     * @param s
     * @return
     */
    public static String toUpperCamelCase(String s) {
        if (s == null) {
            return null;
        }
        s = toCamelCase(s);
        return s.substring(0, 1).toUpperCase() + s.substring(1);
    }

    public static void main(String[] args) {
        System.out.println(CamelCaseUtils.toSnakeCase("ISOCertifiedStaff"));
        System.out.println(CamelCaseUtils.toSnakeCase("CertifiedStaff"));
        System.out.println(CamelCaseUtils.toSnakeCase("UserID"));
        System.out.println(CamelCaseUtils.toSnakeCase("User"));
        System.out.println(CamelCaseUtils.toCamelCase("iso_certified_staff"));
        System.out.println(CamelCaseUtils.toUpperCamelCase("certified_staff"));
        System.out.println(CamelCaseUtils.toCamelCase("user_id"));
    }
}